class Solution {
public:
    TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
        if (root == nullptr) return nullptr;
        if (root == p || root == q) return root;
        TreeNode* left = lowestCommonAncestor(root->left, p, q);
        TreeNode* right = lowestCommonAncestor(root->right, p, q);
        if (left != nullptr && right != nullptr) return root;
        if (left != nullptr) return left;
        if (right != nullptr) return right;

        return nullptr;
    }
};